package org.hjl.commonutils.id;

import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Component;

import java.lang.management.ManagementFactory;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.util.Random;

/**
 * 分布式唯一id
 * 参考了Twitter的SnowflakeId
 *
 * @author hjl
 */
@Slf4j
@Component
public class IdWorkerUtils {

    // 时间起始标记点
    private final static long startTime = 1514736000000L;
    // 机器标识位数
    private final static long workerIdBits = 5L;
    // 数据中心标识位数
    private final static long datacenterIdBits = 5L;
    // 机器ID最大值
    private final static long maxWorkerId = ~(-1L << workerIdBits);
    // 数据中心ID最大值
    private final static long maxDatacenterId = ~(-1L << datacenterIdBits);
    // 毫秒内自增位
    private final static long sequenceBits = 12L;
    // 机器ID偏左移12位
    private final static long workerIdShift = sequenceBits;
    // 数据中心ID左移17位
    private final static long datacenterIdShift = sequenceBits + workerIdBits;
    // 时间毫秒左移22位
    private final static long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
    // 序列号最大值
    private final static long sequenceMask = ~(-1L << sequenceBits);
    // 上次生产id时间戳
    private static long lastTimestamp = -1L;
    // 工作中心id
    private final long workerId;
    // 数据中心id
    private final long datacenterId;
    // 0-并发控制
    private long sequence = 0L;

    /**
     * 无参构造
     */
    public IdWorkerUtils() {
        this.datacenterId = new Random().nextInt(32);
        this.workerId = new Random().nextInt(32);
        log.info("IdWorkerUtils  datacenterId  " + this.datacenterId);
        log.info("IdWorkerUtils  workerId " + this.workerId);
    }

    /**
     * 有参构造
     */
    public IdWorkerUtils(long workerId, long datacenterId) {
        if (workerId > maxWorkerId || workerId < 0) {
            throw new IllegalArgumentException(String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
        }
        if (datacenterId > maxDatacenterId || datacenterId < 0) {
            throw new IllegalArgumentException(String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
        }
        this.workerId = workerId;
        this.datacenterId = datacenterId;
    }

    /**
     * 获取workerId最大值
     */
    private static long getMaxWorkerId(long datacenterId) {
        StringBuilder mpid = new StringBuilder();
        mpid.append(datacenterId);
        String name = ManagementFactory.getRuntimeMXBean().getName();
        if (!name.isEmpty()) {
            // GET jvmPid
            mpid.append(name.split("@")[0]);
        }
        // MAC + PID 的 hashcode 获取16个低位
        return (mpid.toString().hashCode() & 0xffff) % (IdWorkerUtils.maxWorkerId + 1);
    }

    /**
     * 获取数据中心id
     */
    private static long getDatacenterId() {
        long id = 0L;
        try {
            InetAddress ip = InetAddress.getLocalHost();
            NetworkInterface network = NetworkInterface.getByInetAddress(ip);
            if (network == null) {
                id = 1L;
            } else {
                byte[] mac = network.getHardwareAddress();
                id = ((0x000000FF & (long) mac[mac.length - 1])
                        | (0x0000FF00 & (((long) mac[mac.length - 2]) << 8))) >> 6;
                id = id % (IdWorkerUtils.maxDatacenterId + 1);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return id;
    }

    /**
     * 获取下一个ID
     *
     * @return
     */
    public synchronized long nextId() {
        long timestamp = timeGen();
        if (timestamp < lastTimestamp) {
            throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
        }

        if (lastTimestamp == timestamp) {
            // 当前毫秒内，则+1
            sequence = (sequence + 1) & sequenceMask;
            if (sequence == 0) {
                // 当前毫秒内计数满了，则等待下一秒
                timestamp = tilNextMillis(lastTimestamp);
            }
        } else {
            sequence = 0L;
        }
        lastTimestamp = timestamp;
        // ID偏移组合生成最终的ID，并返回ID
        return ((timestamp - startTime) << timestampLeftShift)
                | (datacenterId << datacenterIdShift)
                | (workerId << workerIdShift) | sequence;
    }

    /**
     * 获取时间戳
     *
     * @param lastTimestamp 时间戳
     */
    private long tilNextMillis(final long lastTimestamp) {
        long timestamp = this.timeGen();
        while (timestamp <= lastTimestamp) {
            timestamp = this.timeGen();
        }
        return timestamp;
    }

    /**
     * 获取当前时间戳
     */
    private long timeGen() {
        return System.currentTimeMillis();
    }
}
